JP2000050342A - Method and device for discriminating whether or not radio station is in operation within prescribed geographical range - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology that discriminates whether or not a radio station is in operation within a prescribed geographical position especially in radio communication. SOLUTION: This method and system discriminate whether or not a radio station is in operation within a prescribed geographical position. The method consists of a step where pilot signals are received from plural base stations, a step where a mobile station calculates the time delay between an actual reception time and an estimated reception time of the pilot signals from at least two base stations, a step where the calculated time delay is compared with the time delay stored in advance and a step where it is discriminated that the mobile station is in operation within the prescribed geographical range when the calculated time delay is within the prescribed permissible difference of the stored time delay in advance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates generally to wireless communications. In particular, the invention relates to determining whether a wireless station is operating within a predetermined geographic location.

[0002]

BACKGROUND OF THE INVENTION Wireless telephones are well known in the art.
Generally, a wireless telephone is a mobile station, so that a user can communicate using the telephone anywhere within a particular geographical service area. Continuous communication is provided even when the phone moves within the service area. These continuous services are being used in wireless cellular networks in radio base stations (Radio Base).
Station (RBS) is provided throughout the geographical service area. Each base station serves a geographic area called a cell. As the mobile station moves from one cell to another, continuous service is provided by "handing off" the mobile station from one cell to another. To serve a large number of users, an advanced frequency division plan must be used. The configuration and operation of such a cellular radio system is well known in the art and will not be described in detail here.

Recently, the concept of fixed wireless access has become a concern in the wireless communication arts. In a fixed wireless access system, wireless stations (eg, wireless telephones) are served from a wireless network. However, it is assumed that the radio station is fixed at a predetermined geographic location (eg, the subscriber's home). In fixed wireless systems, more subscribers can be served with less system resources because there is no need to spend system resources on tracking and handing over the movement of wireless stations. In addition, since the location of the fixed radio station is known, interference between users can be better managed, so that the available frequency spectrum can be used more efficiently.

[0004] Thus, fixed wireless subscribers are provided at a lower cost than comparable mobile wireless subscribers. The problem arises in that some wireless telephones can get service from service providers that have both mobile and fixed wireless capabilities. From the service provider's point of view, this is an issue for the service provider to want to distinguish from mobile wireless services. This distinction is made based on the cost or type of service provided. That is, fixed wireless subscribers should be restricted to using the wireless system at the subscriber's fixed location. Also, fixed wireless subscribers have to pay higher rates when using wireless phones as mobile phones outside of their fixed locations.

[0005] In order for a service provider to be able to handle such situations, the location of the radio station must be known. There are several existing techniques for determining the location of a mobile station. For example, in some existing technologies, the location of a mobile station is determined by first calculating the mobile station's distance from at least three base stations and then calculating the geographic location of the mobile station using trigonometry. Can be determined. For example, U.S. Pat. No. 5,646,632 discloses a code division multiple access (Code D).
A technique used in an ivision Multiple Access (CDMA) system is disclosed, in which a mobile station can determine its location using the time delay of a pilot signal received from a nearby base station.

[0006]

SUMMARY OF THE INVENTION Although it is important to determine whether a wireless station is operating within a given geographic location, it has been recognized that it is not necessary to determine the actual geographic location of a wireless terminal. Was. According to the present invention, the determination of whether a wireless station is operating within a predetermined geographic area is made in relation to the propagation delay of a pilot signal transmitted by the base station. Since the actual geographic location of the wireless station is not determined, processing resources are saved over the prior art.

In accordance with the present invention, a radio station receives a pilot signal from a nearby base station during a test process and calculates a time delay between the expected reception time and the actual reception time of the pilot signal. This time delay is determined in relation to a pilot signal from one selected base station, called the reference base station. The time delay is compared to a pre-stored time delay stored in the storage of the wireless station. If the calculated time delay is within a predetermined tolerance of the stored time delay, a determination is made that the wireless station is operating within a predetermined geographic area. The time delay stored in the station's storage is calculated during the initialization process, where the station operates within a given geographic location.

According to one embodiment of the present invention, the comparison between the time delay calculated during the inspection process and the time delay stored during the initialization process is based on the pilot signal of several base stations. This is done by comparing the time delay differences.

In accordance with another embodiment of the present invention, determining whether a radio station is operating in any one of a plurality of predetermined geographic locations includes a time delay calculated during an inspection process;
This is done by comparing a plurality of combinations of time delays, each associated with a plurality of predetermined geographic locations.

[0010] These and other advantages of the present invention will become apparent to those of ordinary skill in the art by reference to the following detailed description and the accompanying drawings.

[0011]

DETAILED DESCRIPTION OF THE INVENTION To illustrate the principles of the present invention, relevant portions of a wireless communication system 100 are shown in FIG. FIG.
Is a wireless station 102 located within a predetermined geographic area 104
(For example, a wireless telephone). The geographic area 104 is an area in which the wireless station 102 can operate and receive fixed wireless access services. For example, geographic area 104 represents the geographic boundary of the subscriber's home. That is, as described in the background above, the wireless station 102 preferably operates within a predetermined geographic area 104.

FIG. 1 also shows base stations 110, 120, 13
0, 140, each of which is associated with a wireless station 10 through a wireless communication link 112, 122, 132, 142, respectively.
Communicate with 2. According to an embodiment of the present invention, the wireless station 102
Communicates with the base stations 110, 120, 130, 140 using a code division multiple access (CDMA) wireless communication protocol. CDMA is a transmission protocol that mixes voice signals with random codes and transmits the resulting signals over a wide band of frequencies using spread spectrum techniques. CDMA transmission protocols are well known in the art and will not be described in detail here.

[0013] Each base station in a CDMA system is a pseudorandom binary sequence.
nce) is transmitted.
Since each base station transmits the same pseudo-random binary sequence, but each base station transmits at a unique time offset,
Each base station can be uniquely identified. More specifically, IS-9
In a 5 system, the pilot signal is an orthogonal pseudo-random binary sequence signal with a period of 32,768 chips.
This is a pseudo random noise of 1.2288 Mcps (Pse
udorandom Noise (PN) corresponds to a period of 26.66 ms due to the chip rate of the sequence. The base station's unique time offset is increased by 64 chips, providing 511 unique offsets. As used herein, reference to one of the 511 unique offsets is made when referring to the unique offset of the base station. That is, a reference to a base station unique offset of 10 is actually an offset of 640 (64 × 10 = 640) chips. Those skilled in the art will appreciate that the principles of the present invention may be implemented in systems having different chip rates.

Referring to FIG. 1, base station 110 transmits a pseudo-random binary sequence at offset 84, base station 120 transmits a pseudo-random binary sequence at offset 8, and base station 130 transmits a pseudo-random binary sequence at offset 164. Transmitting a binary sequence, base station 140 transmits a pseudo-random binary sequence at offset 34.

The reception of a pilot signal at a radio station is delayed by a propagation delay. As shown in FIG.
The propagation delay of the pilot signal from 10 to the mobile station 102 is 1 chip, the propagation delay of the pilot signal from the base station 120 to the mobile station 102 is 3 chips, and the base station 13
The propagation delay of the pilot signal from 0 to the mobile station 102 is 2
And the propagation delay of the pilot signal from the base station 140 to the mobile station 102 is 10 chips. As described in further detail below, the present invention uses this information to determine whether the wireless station 102 is within a predetermined geographic area 104.

FIG. 2 is a block diagram showing components of the wireless station 102 constructed according to the present invention. A transceiver 204 that transmits and receives signals from an antenna 202
Is included. The overall functions of wireless station 102 are controlled by control processor 206, which operates by executing computer program instructions stored in program and data storage 208. Wireless station 102
It is this program instruction that defines the overall operation of. The program and data storage 208 also stores other data required for operation of the wireless station 102, such as user preferences, user telephone numbers, communication provider IDs, and wireless station IDs. In addition, since the program and data storage device 208 is at least partially non-volatile, the information it contains remains after the wireless station 102 has been powered down. Although FIG. 2 shows the program and data storage device 208 as one component, those skilled in the art will appreciate that the program and data storage device 208 is implemented as a separate storage unit. You can understand.

The wireless station 102 also includes a keypad 210 to enable communication between a user and the control processor 206. The audio information transmitted by the wireless station 102 is received through a microphone 212, and the audio information received by the wireless station 102 is reproduced to a user through a speaker 214. The wireless station 102 also includes a display 216 that allows the control processor 206 to display alphanumeric data to a user. It should be understood that this block diagram is for illustrative purposes only. The design and operation of wireless systems are well known in the art and various modifications are possible.

The steps performed by wireless station 102 in accordance with the present invention will be described with reference to the flowcharts of FIGS. These steps are performed under the control of control processor 206, which executes computer program instructions stored in program and data storage 208. According to the present invention, the wireless station first determines whether it is within the predetermined geographical area by performing a measurement that is within the predetermined geographical area and storing a numerical value in the storage of the wireless station. I do. These steps are called initialization processing, and are shown in the flowchart of FIG. Thereafter, when the wireless station desires to obtain service, or periodically, the wireless station makes certain measurements and compares the measurements to the values stored during the initialization process. These steps are called inspection processing and are shown in the flowchart of FIG. 3 and 4
The steps of the flowchart of FIG. 4 are described together with the example of the wireless station 102 and the base stations 110, 120, 130, 140 in FIG.

Referring now to the flowchart of FIG. 3, the steps of the initialization process will be described. Step 30
At 4, the wireless station 102 is connected to nearby base stations 110, 120,
It receives pilot signals from 130 and 140 and locks on the strongest pilot signal. For the purpose of this description, it is assumed that the strongest pilot signal is received from base station 140 and that wireless station 102 locks onto this pilot signal. Base station 140 is called a reference base station. In step 306, the wireless station 102 receives the pseudo-random binary sequence offset transmitted by the base station 140. This offset is included as part of the pilot signal transmitted by the reference base station 140. As shown in FIG. 1, the offset of the base station 140 is 34 (ie, 34 × 64 = 2
176 chips). Therefore, base station 140 transmits a pseudo-random binary sequence at 2176 chips after the zero reference time. Upon receiving this information, the wireless station 102 synchronizes its operation with the operation of the base station 140 in step 308. Knowing the base station offset, the wireless station 102 can determine the zero reference time by noting the base station's pseudo random binary sequence reception time. Note, however, that there is a signal propagation delay from base station 140 to wireless station 102. This propagation delay is shown as 10 chips in FIG. Therefore, the wireless station 102
Is delayed by 10 chips. As a result, when the wireless station calculates the propagation delay of the pilot signal of another base station, the calculation is delayed by 10 chips. Therefore, the wireless station 102
All subsequent calculations of propagation delay are based on the offset received from the reference base station and the actual propagation delay of the pilot signal from the reference base station.

Referring again to FIG. 3, at step 310, wireless station 102 receives a pseudo-random binary sequence offset of a base station adjacent to reference base station 140. This information is provided to wireless station 102 by a pilot signal transmitted by reference base station 140. In the example shown in FIG. 1, the pilot signal of the reference base station 140 has an offset of 8 for each of the adjacent base stations 110, 120 and 130.
Assume that they are identified as 4, 8 and 164. Now, knowing the pseudo-random binary sequence offset of the neighbor base station, the wireless station 102 looks for those pilot signals in step 312 and calculates the propagation delay of the pilot signals. When looking for a pseudo-random binary sequence with an offset, the wireless station 102 looks at the time window of the pseudo-random binary sequence. If a pseudo-random binary sequence is found within the time window, the wireless station assumes that the signal is from the identified neighboring base station. That is, the time window is selected such that it is large enough to compensate for the propagation delay of the signal, but not so large that the pseudo-random binary sequence falls within the time transmitted by any other base station. The size of this time window depends on the cell coverage radius and pilot
Determined as a function of offset reuse. The pilot offset of one cell is reused in another cell. However, in a properly planned system, such other cells are far enough away from one cell that the pilot signal from the other cell is very weak and will not cause a problem in one cell.

It should also be noted here that all measurements performed by the radio station are distorted by the propagation delay of the pilot signal transmitted by the reference base station. Consider the example shown in FIG. The base station 110 calculates 84,
That is, it is assumed that it is specified as an adjacent base station having an offset of 5376 (84 × 64) chips. Because there is a one-chip propagation delay from base station 110 to wireless station 104, wireless station 104 actually receives a one-chip pilot signal after an offset of 84. However, since the synchronization of the radio station 102 is shifted by 10 chips as described above, the radio station 102 receives the pilot signal from the base station 110 9 chips earlier, that is, as having a propagation delay of -9 chips. Think you did. That is, as can be seen from this example, since the reference base station is used to synchronize the radio stations, the subsequent propagation delay calculation performed by the radio station is related to the propagation delay of the pilot signal transmitted by the reference base station. Will be determined.

Returning now to step 312 of FIG. 3, it is calculated that the propagation delay of base station 110 is -9.
In a similar manner, the propagation delay of base station 120 is calculated to be -7, and the propagation delay of base station 130 is calculated to be -8. Since the base station 140 is a reference base station, the propagation delay of the base station 140 is zero. Step 31
At 4, the propagation delay is stored in a table in the non-volatile portion of the storage device 208 (FIG. 2) of the wireless station 102. This table is shown below as Table 1.

[0023]

[Table 1] The initialization process ends at step 316. Note that these initialization steps are performed when it is desired to initialize a predetermined geographic area of the wireless station 102. For example,
These steps are performed when the wireless station 102 is used for the first time within a predetermined geographic area. Also, these steps are performed periodically and may re-establish a predetermined geographic area of the wireless station 102. According to the example described herein, the information stored in Table 1 defines a predetermined geographic area of wireless station 102 as area 104 (FIG. 1).

According to the present invention, when wireless station 102 desires to obtain service from wireless communication system 100, Table 1 is used to determine if it is operating within a given geographic area 104. The steps performed by the wireless station 102 before obtaining service are called inspection processes and are shown in FIG. Steps 404-412 are the same as steps 304-312 described above in connection with FIG. After performing step 412, the mobile station has a table of newly calculated propagation delays for neighboring base stations stored in storage device 208, similar to Table 1. For example, assume that the wireless station locks to base station 140 as a reference base station, and that the following Table 2 is obtained as a result of the propagation delay calculations performed during the inspection process.

[0025]

[Table 2] Note that Table 2 contains the same values as Table 1.
In step 414 (FIG. 4), the wireless station 102
12 is stored in the storage device 2 of the wireless station 102.
08 with the propagation delay stored. This comparison step is performed by comparing the difference in propagation delay of the combination of base stations. For example, base station 110 and base station 12
Consider a combination of 0 base stations. Referring to Table 1, the difference between the propagation delays of the base stations in this combination is -2.
(-9-(-7)). Similarly, base stations 110 and 1
The difference between the propagation delays of the 30 combinations is −1, and the difference between the propagation delays of the combinations of the base stations 120 and 130 is 1. Of course, the difference between the propagation delays of these combinations is the same as the information in Table 2. Since all numbers are the same, the comparison is within the required tolerance and the test in step 416 determines that Y
Because it is an ES, control is passed to step 420 where the wireless station is determined to be operating within a predetermined geographic area. The service provider can take appropriate steps, such as providing a service to the wireless station 102.
If the test at step 416 is NO, step 418 determines that the wireless station is not operating within a predetermined geographic area. In that case, the service provider may take appropriate steps, such as denying service to the wireless station 102. For example, when performing step 418, wireless station 102 may prohibit a call from originating or terminating at the wireless station. Further, if the steps of the inspection process are performed periodically, the wireless station may abort an existing call if the wireless station 102 has moved out of a predetermined geographic area.

Although the wireless station 102 is operating within a given geographical location 104, it is possible that the propagation delay calculated in step 412 may be slightly different from that stored in Table 1 as storage. One reason for the differences in the calculated propagation delays is a change in environmental conditions that results in multipath fading and / or changes in the signal-to-noise ratio. For example, assume that the propagation delay calculated in step 412 is shown in Table 3 below.

[0027]

[Table 3] In this case, the difference in propagation delay between the combinations of the base stations during the inspection process and the initialization process is shown in Table 4 below. In this table, the first column indicates the combination of base stations considered. The second column shows the propagation delay calculated during the inspection process. The third column shows the propagation delay calculated during the initialization process. The fourth column shows the difference in propagation delay between the inspection processing and the initialization processing.

[0028]

[Table 4] That is, the wireless station 102 continues to operate in the predetermined geographic area 1
Operating within 04, the measured propagation delay calculated during the inspection process is somewhat different from that stored during initialization of wireless telephone 102. Therefore, step 416
Tests compare the delays to determine if they are within a certain tolerance. For example, if the tolerance is set to allow a deviation of up to one chip for any combination of two base stations, the measurements shown in Table 4 pass the test in step 416. The allowable value is set by the service provider in consideration of the operating environment of the wireless station 102.

Even if the wireless station 102 is operating within a predetermined geographic area 104, the wireless station 102
When performing step 4, i.e., each time it locks to the strongest pilot signal during the inspection process, it is possible to lock to a different base station pilot signal. For example, assume that a wireless station has locked onto base station 110 during a particular operating session. In this case, the base station 110 becomes the reference base station, and the propagation delay calculated in step 412 is as shown in Table 5 below.

[0030]

[Table 5] Proceeding to step 414, the wireless station 102
At 12, the propagation delay calculated during the inspection process is compared with the propagation delay stored in the storage device 208 of the wireless station 102 during the initialization process. As explained above, this comparison step is performed by comparing the propagation delay differences of the combinations of base stations. Table 6 below shows this comparison.

[0031]

[Table 6] Since all differences are zero, the test in step 416 is Y
ES, and control proceeds to step 420 where the wireless station 10
2 is determined to be within the predetermined geographic area 104. That is, although the reference base station has changed from 140 during the initialization process to 110 during the inspection process, the technique of the present invention also applies to the radio station since the comparison of step 416 tests the difference in propagation delay of the combination of base stations. 102 is a predetermined geographic area 10
Then, it is determined whether or not the operation is performed in Step 4.

According to another embodiment, the techniques of the present invention can be used to determine whether mobile station 102 is within one of a plurality of predetermined geographic areas. In this embodiment, the initialization process of FIG. 3 is repeated while the wireless station 102 is within each predetermined geographic area, and the propagation delay calculated for each area is stored in a separate table in non-volatile storage. You. Accordingly, during the inspection process of FIG.
This is repeated for each table stored in the non-volatile storage device. YES at step 416 for any table
If so, the wireless station 102 is determined to be operating within a predetermined geographic area associated with the table.

The above detailed description is in all respects only illustrative, not restrictive, and the scope of the invention disclosed herein is not limited by the detailed description, but rather by the full scope permitted by the patent statutes. It is determined by the appended claims, which are to be construed broadly. The embodiments shown and described herein are merely illustrative of the principles of the present invention, and various modifications may be made by those skilled in the art without departing from the scope and spirit of the invention. Please understand that.

[Brief description of the drawings]

FIG. 1 is a diagram showing relevant parts of a wireless communication system.

FIG. 2 is a diagram showing a block diagram of components of a wireless station configured according to the present invention.

FIG. 3 is a flowchart illustrating steps performed by a wireless station during an initialization process.

FIG. 4 is a flowchart illustrating steps performed by a wireless station during an inspection process.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Jeffrey Ross Wright United States 60646 Illinois, Lincolnwood, North Kildare Avenue 7331 (72) Inventor Mark Kevin Stockard United States 60190 Illinois, Winfield, Churchill Road 26 W 440 (72) Inventor Charles Varvaro United States 60139 Illinois, Glendale Heights, Burdett Ave New 22 W 410

Claims (17)

[Claims] 1. A method for determining whether a mobile station is operating in a predetermined geographic area, comprising: receiving a pilot signal from a plurality of base stations; Calculating a time delay between an expected reception time and an actual reception time of the pilot signal from a station; comparing the calculated time delay with a previously stored time delay; Determining that the mobile station is operating within the predetermined geographic area if the time delay is within a predetermined tolerance of the pre-stored time delay. 2. The method of claim 1, wherein said expected reception time of said pilot signal is determined in relation to a pilot signal received from a selected one of said base stations. how to. 3. The method of claim 1, wherein the comparing step further comprises comparing the difference between the time delays of the pilot signals of the base station combinations. 4. The method of claim 1, wherein the pre-stored time delay comprises a combination of time delays.
Each of the time delay combinations is associated with one of a plurality of predetermined geographical areas, and the comparing step further comprises comparing the calculated time delay to a previously stored combination of time delays. The determining step further comprises: when the calculated time delay is within a predetermined tolerance of a set of pre-stored time delays associated with the one of the plurality of predetermined geographic areas. Determining that the mobile station is operating within one of the plurality of predetermined geographic areas. 5. The method of claim 1, wherein the method further comprises: when the calculated time delay is not within a predetermined tolerance of the pre-stored time delay. A method comprising: determining that the mobile station is not operating within a geographic area; and denying service to the mobile station. 6. The method according to claim 5, wherein the comparing step and the determining step are performed periodically during the presence of the call, and the step of denying the service further comprises aborting the existing call. A method comprising the steps of: 7. A method for determining whether a mobile station is operating in a predetermined geographic area, comprising: a plurality of base stations during an initialization session in which the mobile station operates in the predetermined geographic area. Receiving a pilot signal from the mobile station; calculating a time delay between an expected reception time and an actual reception time of the pilot signal from the at least two base stations at the mobile station; Storing the calculated time delay in a storage device; receiving a pilot signal from a plurality of base stations during a test session following the initialization session; and Calculating the time delay between the expected reception time and the actual reception time of the pilot signal from the base station; a) piloting the base station combination calculated during the test session; Comparing the difference between the time delays of the signals and b) the difference between the stored time delays of the pilot signals of the base station combination calculated during the initialization session; and the result of the comparing step Determining that the mobile station is operating in a predetermined geographical area if is within a predetermined tolerance. 8. The method of claim 7, wherein the expected reception time of the pilot signal is determined in relation to a pilot signal received from a selected one of the base stations. how to. 9. The method of claim 8, wherein the selected one of the base stations is the same during the initialization session and during the test session. 10. The method of claim 8, wherein the selected one of the base stations is different during the initialization session and during the test session. 11. The method of claim 7, further comprising: if the result of the comparing step is not within a predetermined tolerance, the mobile station is not operating in the predetermined geographic area. A method comprising: determining; and denying service to the mobile station. 12. The method of claim 11, wherein the steps of the testing session are performed periodically during the presence of a call, the step of denying the service further comprising the step of aborting the existing call. Including methods. 13. A receiver for receiving a pilot signal from a plurality of base stations, and wherein the mobile station determines a time delay between an expected reception time and an actual reception time of the pilot signal from at least two of the base stations. Means for calculating; a storage device for storing a reference time delay; means for comparing the calculated time delay with the stored reference time delay; and calculating the calculated time delay for the stored reference time delay. Means for determining that the mobile station is operating within a predetermined geographical area when within a predetermined tolerance. 14. The mobile station of claim 13, wherein the reference time delay is stored as a combination of time delays, each of the combinations being one of a plurality of predetermined geographic areas.
A mobile station characterized in that: 15. The mobile station of claim 14, wherein the comparing means further comprises means for comparing the calculated time delay with the combination of time delays, and wherein the determining means further comprises the calculated time delay. When the time delay is within a predetermined tolerance of a stored reference time delay associated with the one of the plurality of predetermined geographic areas, the mobile station is configured to determine whether the mobile station is in one of the plurality of predetermined geographic areas. A mobile station comprising means for determining that the mobile station operates. 16. The mobile station according to claim 13, wherein
The mobile station further comprises means for determining that the mobile station is not operating within the predetermined geographic area when the calculated time delay is not within a predetermined tolerance of the stored reference time delay. And means for refusing service to the mobile station. 17. The mobile station according to claim 16, wherein
The rejection step further comprises the mobile station comprising means for aborting the existing call.